The invention relates to a transmission and reception module for bidirectional optical message and signal transmission, in which a fiber connection for an optical fiber and lens coupling optics are disposed in a common housing. Such modules include a first optical unit, which contains a transmitter, is disposed on the longitudinal axis of the housing defined by the fiber axis. Such modules include at least one beam splitter disposed at an oblique angle to the longitudinal axis, and on the longitudinal axis, in the interior of the housing. By means of the beam splitter, it is possible to deflect beams of light radiation from and to at least one corresponding further optical unit. These optical units disposed to the side of the longitudinal axis. For many years, fiber-optic message transmission used transmission of at least one channel in each case, bidirectionally, using the full-duplex or half-duplex method. By way of example, European Patent Application 0 463 214 A1 discloses a transmission and reception module, which is known as a BIDI module, for bidirectional optical message and signal transmission. In this module, the two active components (the light transmitter and the light receiver) are installed as autonomous components encapsulated such that they are hermetically sealed in a common module housing. In a hollow interior of the common module housing, a beam splitter and lens coupling optics are disposed. The module also includes a fiber connection for a common optical fiber. The transmitter injects an optical signal into the attached glass fiber, while another optical signal can be received from the same fiber simultaneously or at a different time. The beam splitter separates the two signals. The beam splitter also may contain a WDM (wavelength division multiplexing) filter, in which one specific wavelength can be reflected, and another can be passed.
If, apart from the respective one channel in each direction, it is intended to transmit a further channel in at least one direction, then an external fiber splitter or an external WDM filter can be installed in the supplying glass fiber. This glass fiber can be located upstream of the module. However, this represents a relatively impracticable solution.
On the other hand, a so-called multichannel transceiver module is proposed in German Published, Non-Prosecuted Patent Application DE 93 114 859 A1. In this application, at least one further light transmitter and/or light receiver with associated lens coupling optics and at least one further beam splitter are provided in the common housing of a conventional BIDI module as described above. The further light transmitter or transmitters and/or light receiver or receivers is or are designed preferably in the form of the so-called TO (transistor outline) standard construction. TO standard construction has been described in German Published, Non-Prosecuted Patent Application DE 93 120 733 A1. However, this solution has the disadvantage that bidirectional transmission of a further channel requires two TO modules, namely a transmission module and a reception module, in the common housing.
European Patent Application 0 644 668 A1 discloses a transmission and reception module for bidirectional optical multichannel transmission having a light transmitter, a light receiver, a fiber connection for a common optical fiber, lens coupling optics, and a beam splitter. The beam splitter is positioned at an intermediate point in the beam path, and is disposed in a common housing. At least one further light transmitter and/or light receiver, with associated lens coupling optics, and at least one further beam splitter are provided in the common housing. In the illustrated exemplary embodiments, the beam splitters are disposed one behind the other in the beam path, and parallel to one another, inclined at an angle of 45xc2x0 to the beam path, between the fiber connection and the opposite light transmitter, in the axial direction of the optical fibers in the housing.
European Patent Application 0 487 391 A1 relates to an optical bidirectional transmission and reception module having a common fiber connection opening, a plurality of transmitters, a plurality of receivers, and a corresponding plurality of light paths. Beam splitters are in each case disposed upstream of the transmitters and receivers in two mutually parallel levels. The object of this arrangement of beam splitters is to allow light at a wavelength corresponding to the respective transmitter or receiver to pass, and to reflect light at all other wavelengths.
A compact bidirectional transmission and reception device is disclosed in U.S. Pat. No. 5,416,624. The compact bidirectional transmission and reception device has a planar convex lens with a beam-splitting wavelength filter disposed on its planar surface. This lens is positioned between a transmitter and a receiver. This arrangement produces a compact transmission and reception device. In addition, in FIG. 4, this document shows a linear array of such lenses, by means of which radiation beams from such a linear arrangement of transmitters can be injected into a linear arrangement of optical fibers.
Accordingly, the object of the present invention is to specify a transmission and reception module having a multichannel capability for bidirectional optical message and signal transmission. This reception module also is designed to save space and expand by adding further bidirectional channels in as simple a manner as possible.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a transmission and reception module for bidirectional optical message and signal transmission. This module features a common housing forming an opening and containing lens coupling optics and a fiber connection for an optical fiber with a longitudinal axis. The module also includes a first optical unit containing a transmitter disposed along the longitudinal axis. In addition, the modules includes a second optical unit adjacent the longitudinal axis, at least one of said first optical unit and said second optical unit being a combined transmission/reception unit having a unit housing at least partially surrounding a transmitter and a receiver, the unit housing mounted in said opening in said common housing. The module further includes a beam splitter in said common housing disposed on the longitudinal axis and at an oblique angle thereto. The beam splitter deflects beams of light radiation between said first optical unit and said second optical unit.
The invention described further below with reference to exemplary embodiments achieves this object in a compact module in which at least one transmitter and at least one receiver are combined in a transmission/reception unit. This unit is installed in the common housing. Furthermore, at least one additional such transmission/reception unit or at least one transmission unit or one reception unit are provided in the common housing.
In one preferred embodiment of the present invention, the transmission/reception unit is designed in accordance with a bidirectional transceiver module which is described in German Published, Non-Prosecuted Patent Application DE 93 120 733 A1 and is also referred to as a TO-BIDI module. Furthermore, the at least one transmission unit or the at least one reception unit is preferably designed as a TO module. The invention thus describes a compact module that combines the assemblies of the known BIDI module and those of the TO-BIDI module with their characteristics.
The multichannel BIDI thereby produced can transmit one channel, or more than one channel, in the respective directions simultaneously, in addition to the normal bidirectional function on two bidirectional channels.
A conventional BIDI module having two bidirectional channels, that is to say one transmission channel and one reception channel, thus becomes a module with three channels by the use of a TO transmission or reception module by means of a TO-BIDI having the same external dimensions. If one TO transmission module is replaced by a TO-BIDI, one transmission and reception channel and a second reception channel result. If one TO reception module is replaced by a TO-BIDI, the configuration produces two transmission channels and one reception channel. Finally, if a TO laser and TO receiver are each replaced by TO-BIDIs, then the configuration produces two transmission and two reception channels: i.e., four channels. This can, of course, also be expanded to the module arrangement having three TO components, resulting in modules with five and six channels. The corresponding expansion to even more channels can be achieved by appropriate lengthening of the module by simultaneous outputting by means of additional filters in the optical beam path to the corresponding additional TO components. In optical terms, this can be done in a particularly simple manner by designing the optics of the TO components for one collimated beam in the module. The maximum possible number of channels is thus twice as great as the number of connected TO-BIDIs, or is correspondingly less if a single TO transmission or reception component is used instead of a TO-BIDI.
A further major advantage of the arrangement according to the invention is that the optical channel separations in the TO-BIDI and BIDI module can be of a different type or of the same type. If, for example, a WDM filter is used for virtually no-loss separation of two wavelengths in the module, then not only can the separation in the TO-BIDI be accomplished in the same way once again, using a WDM filter to two further wavelengths. However, a 3 dB-beam splitter can also be used to split the intensity of one wavelength between, in each case, one reception channel and one transmission channel.
This means that the use of TO-BIDIs as TO components allows the multichannel BIDI to operate each individual channel bidirectionally. This is true particularly in the case of WDM systems having a number of discrete wavelengths: for example, in accordance with the ITU Standard, four wavelengths or even more. These are so-called HD-WDM systems. In comparison with multichannel HD-WDM systems as normally used until now, and which are operated only unidirectionally, this results in full bidirectional functionality on each WDM channel. This means that, for relatively recent multichannel WDM transmission on individual glass fibers, the arrangement according to the invention allows the transmission capacity of the fibers to be doubled by means of bidirectional operation.
Thus, using the arrangement according to the invention, two bidirectional module types with different optics are combined such that a new module type is produced. The functional characteristics of this new module are considerably better than the intrinsic functions of the individual module types. Thus, using the arrangement according to the invention, it is not just possible to produce any desired multichannel modules, but also to operate one-directional multichannel HD-WDM transmission systems fully bidirectionally. The wavelength stabilization which is required, for example by means of temperature stabilization, can in this case be accomplished by appropriate temperature stabilization of the entire module, as described, for example, in German Published, Non-Prosecuted Patent Application DE 93 114 860 A1.
In accordance with another feature of the invention, the combined transmission/reception unit includes a combined mirror/beam-splitter layer equally reflecting a radiation beam emitted from the transmitter and transmitting a received radiation beam that is to be detected by the receiver.
In accordance with another feature of the invention, the transmission/reception module further includes a common substrate supporting the lens coupling optics and the transmitter. The transmitter is a laser chip having a light output side opposing a substrate part mounted on the common substrate. The common substrate holds the combined mirror/beam-splitter layer. The combined mirror/beam-splitter layer inclines at an angle of approximately forty-five degrees (45xc2x0) to the light output side of the laser chip such that a radiation beam which is emitted by the light output side is reflected on the combined mirror/beam-splitter layer toward the lens coupling optics. The substrate part and the common substrate transmit a wavelength of the received radiation beam to be detected by the receiver, and the light receiver located on the outlet side of the received radiation beam from the common substrate.
In accordance with another feature of the invention, the beam splitter can contain a selective-wavelength filter.
In accordance with another feature of the invention, the transmission/reception unit further includes a common substrate having a bottom face and a substrate part. The substrate part having a side surface with a mirror layer. The transmission/reception unit also includes a laser chip below the optical coupling having a resonator surface emitting a radiation and. The laser chip is disposed as a transmitter with the side surface adjacent the resonator surface. The resonator surface inclines at an angle of approximately forty-five degrees (xcx9c45xc2x0) to the side surface so the radiation is directed upwards perpendicularly from the common substrate to the lens coupling optics. The lens coupling optics attaches to the substrate part such that the mirror layer is adjacent the resonator surface. The beam splitter reflects the radiation emitted from the laser chip and passing radiation injected from the lens coupling optics such that the light receiver is provided underneath the beam splitter, on the bottom face of the common substrate.
In accordance with another feature of the invention, the transmission/reception module can include a reception unit; a transmission unit; a further transmission/reception unit; two reception units; a reception unit and a further transmission/reception unit; four reception units; four transmission units; and/or four further transmission/reception units.
In accordance with another feature of the invention, the transmission/reception module can include 2n further transmission/reception units, where n is an integer greater than or equal to 2.
Although the invention is illustrated and described herein as embodied in a bidirectional module for multichannel use, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.